to Dr. IV>reen Stranger, Miss Kahan and Messrs. Awroiraixi, Henderson, Menaces, McCorinick and Ogden, students in the Anatomy Department of University College, for their assistance in the work of dissection.
I am indebted to Professor Elliot Smith, Mr. E. I. Pocock, and the Publication Committee of the Zoological Society of London for permission to reproduce illustrations. Figures numbered 11, 12 and 19 to 57 are original, and were drawn under mv supervision by my assistant, Mr. C. H. Hicks, to whom I express my thanks. Figure 5 is from a photograph by Mr. W. E. Le G-ros Clark, F.B.C.&.. and all other illustrations of living animals are from photographs by Mr. H. Bond of the Zoological Society.
C. E1. SONNTAG,
Zoological Society of London, October 25, 1923.